Mandalay Bay is one of my favorite hotels in Vegas. There's just something about the atmosphere here.
The size of rooms are above average by Vegas standards. The bathrooms are large and even have small TVs in them. The casino is laid out well. The wave pool and lazy river are great. I always get a good rate when I go there and sometimes I get comped.
The M-Life players club card is worth getting, even if you don't gamble. Use it there and at all of the MGM owned Vegas hotels when you go out to eat and charge it to the room. This gets you points.
There are 3 downsides to this hotel. 1) It's on the very south end of the strip. 2) There are no hotels across the street. The only hotel near it is the Luxor which is actually connected to it by the mall Mandalay Place. 3) During the summer there are a lot of kids at the pool (beach). I'd rather see people there around my age.
If it's pool season next time I'm in Vegas I want to go to the new pool party called Light. I peaked in there and it looks like a lot of fun. I also spent a few minutes at Light Nightclub. It looked amazing and I want to go back there.